JP2009150106A - Beam-column frame - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a beam-column frame which is of a reinforced concrete structure, and contributes to reduction of material costs. <P>SOLUTION: The beam-column frame K2 of the reinforced concrete structure is set up by arranging first beam main reinforcements 5a crossing a boundary surface J between a column 1 and a beam 5, and second beam main reinforcements 5b not crossing the boundary surface J, and superposing the first beam main reinforcements 5a and the second beam main reinforcements 5b on each other at a longitudinal end of the beam 5. Herein a design-basis strength of concrete at the longitudinal end of the beam 5 is set by taking into consideration in terms of structure design, that part of compressive force occurring at the longitudinal end of the beam 5 attributable to bending moment acting on the beam 5, is borne by the second beam main reinforcements 5b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a column beam frame having a reinforced concrete structure.

  In a column beam frame composed of a reinforced concrete structure, a beam main bar is generally arranged so as to cross the boundary surface between the column and the beam, and the beam main bar is fixed inside the column.

  The cross-sectional design of a beam composed of reinforced concrete is that the compression force generated by the bending moment is borne by the compression beam concrete and the compression concrete, and the tensile force is borne by the tension beam principal. This is usually done on the assumption. Incidentally, in many cases, the cross-sectional design of a beam is performed with respect to the bending moment at the time of an always-on-earthquake occurring at the interface with the column.

  In order to avoid brittle bending compression failure, it is necessary to precede the yielding of the main beam on the tensile side, so the compressive strength of the concrete is of a magnitude that matches the tensile force borne by the tensile beam on the tensile side. It is necessary to set so as not to cause compressive failure due to compressive force. For this reason, in high-rise buildings where a large tensile force acts on the beam main bar on the tension side, high-strength concrete is used so that a compressive force that balances the large tensile force can be borne. Concrete has a problem that its construction cost increases because its material cost is higher than that of ordinary strength.

  Even if high-strength concrete is required for the beam, normal-strength concrete is often sufficient for the floor slab, so the beam and floor slab should be made of concrete so that the material cost does not increase. Although there are cases where they are divided, there is a problem that it takes time to install and remove the mold necessary for the arrangement.

  Moreover, since high-strength concrete is higher in viscosity than ordinary strength, there is also a problem that it takes time to level the placing surface. As disclosed in Patent Documents 1 to 3, etc., if the lower half of the beam is composed of a precast member made of high-strength concrete, and high-strength concrete is placed on the upper side of this precast member, high strength However, if there is a cast-in-place concrete part at the end of the beam, there is no change in using high-strength concrete with a high material cost.

Japanese Patent No. 3552117 JP 2006-97320 A JP 2006-225894 A

  From such a viewpoint, it is an object of the present invention to provide a column beam frame having a reinforced concrete structure and capable of keeping material costs low.

  A first column beam frame according to the present invention that solves such a problem includes a first beam main bar that crosses a boundary surface between a column and a beam, and a second beam main bar that does not cross the boundary surface. A column beam structure of a reinforced concrete structure in which the first beam main bar and the second beam main bar are overlapped at the end in the longitudinal direction, and the end in the longitudinal direction of the beam due to a bending moment acting on the beam In consideration of the structural design that the second beam main reinforcement bears a part of the compressive force generated in the part, the design standard strength of the concrete at the end in the longitudinal direction of the beam is set. To do.

  If the ratio of tensile reinforcement (= cross-sectional area of tensile reinforcement / (beam width x effective beam)) is the same, the larger the double reinforcement ratio (= compression reinforcement cross-sectional area / tensile reinforcement cross-sectional area), the more concrete is required. Where the compressive strength is reduced, according to the present invention, the double reinforcement ratio of the beam can be increased without increasing the tensile reinforcement ratio at the boundary surface. It is smaller than the column beam frame. That is, the second beam main bar that does not cross the boundary surface bears only the compressive force without bearing the tensile force generated at the boundary surface, so only the double muscle ratio is increased without increasing the tensile reinforcement ratio at the boundary surface. Can be increased.

  Thus, according to the present invention, since the compressive force borne by the concrete of the beam is smaller than the beam of the conventional column beam frame, it is possible to use less expensive concrete than high-strength concrete, As a result, material costs can be kept low.

  Moreover, the second column beam frame according to the present invention for solving the above-mentioned problems is provided with a beam main reinforcing bar and a compressive force bearing reinforcing bar different from the beam main reinforcing bar, and the beam main reinforcing bar at the longitudinal end portion of the beam. And the compressive force bearing rebar, which is a reinforced concrete column beam structure, in which the compressive force bearing rebar is provided so as not to cross the boundary surface between the column and the beam, and a bending moment acting on the beam is provided. In consideration of the structural design that the compressive force bearing rebar bears a part of the compressive force generated at the longitudinal end portion of the beam due to the structural design, the design standard of the concrete at the longitudinal end portion of the beam The strength is set.

  According to this column beam structure, the compressive force-bearing rebar that does not cross the boundary surface bears only the compressive force without bearing the tensile force generated at the boundary surface, so the ratio of the tensile rebar of the beam at the boundary surface is Only the double bar ratio of the beam can be increased without increasing. That is, according to the present invention, the compressive force borne by the concrete of the beam is smaller than that of the beam of the conventional column beam frame, so that it is possible to use concrete that is less expensive than high-strength concrete. Material costs can be kept low.

In addition, a third column beam frame according to the present invention that solves the above-described problems includes a first beam main bar that crosses a boundary surface between a column and a beam, and a second beam main bar that does not cross the boundary surface. Columnar frame of a reinforced concrete structure in which the first beam main bar and the second beam main bar are overlapped at the end in the longitudinal direction of the column, and the design standard strength of the concrete used for the column is 60 N / mm ^2. That is the above, and the design standard strength of the concrete used for the end portion in the longitudinal direction of the beam is 36 N / mm ² or less, and used for the floor slab of the reinforced concrete structure connected to the side surface of the beam. It is characterized by being equal to the design standard strength of concrete.

The third beam structure is designed by considering that the second beam main bar bears a part of the compressive force generated at the end of the beam in the longitudinal direction due to the bending moment acting on the beam. This is a novel and new column beam structure. According to this column beam structure, the design standard strength of the concrete used for the column is set to 60 N / mm ² or more, while the design standard strength of the concrete used for the end portion in the longitudinal direction of the beam is set to 36 N / mm ^2. Since the following is used, the material cost can be kept low. In addition, the concrete design standard strength of the concrete used for the longitudinal ends of the beams was made equal to the concrete design standard strength of the concrete used for the floor slabs. Is possible. That is, according to the present invention, it is not necessary to separate the concrete between the beam and the floor slab, and the installation / demolding work of the mold necessary for the placement is not required.

  Further, a fourth column beam frame according to the present invention for solving the above-mentioned problems is provided with a beam main bar and a compressive force bearing reinforcing bar different from the beam main bar, and the beam main bar at an end portion in the longitudinal direction of the beam. And the compressive force bearing reinforcing bars are reinforced concrete column beam frames, wherein the compressive force bearing reinforcing bars are provided so as not to cross the boundary surface between the columns and the beams, and the longitudinal ends of the beams The design standard strength of the concrete used in the construction is equal to the design standard strength of the concrete used for the floor slab of the reinforced concrete structure connected to the side surface of the beam.

  The fourth column beam frame is a novel and new column beam frame having a compressive force bearing rebar different from the beam main bar. According to this column beam structure, it becomes possible to place concrete on the beam and the floor slab at the same time. That is, according to the present invention, it is not necessary to separate the concrete between the beam and the floor slab, and the installation / demolding work of the mold necessary for the placement is not required.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to hold down the material cost of the column beam frame which consists of a reinforced concrete structure.

(First embodiment)
The column beam frame K1 according to the first embodiment is a column beam frame applied to a high-rise building having a height of 60 m or more (in the case of an apartment, 20 stories or more), and is shown in FIG. Thus, it is configured to include a column 1 and a beam 2. Further, as shown in FIG. 1B, a floor slab 3 is integrally connected to the side surface of the beam 2. In FIG. 1, the column main bars and the slab bars are not shown.

The column 1 has a reinforced concrete structure and includes a plurality of column main bars arranged in the vertical direction. Although there is no restriction | limiting in the mixing | blending, strength, etc. of the concrete used as the pillar 1, In this embodiment, it is set as the high intensity | strength concrete whose design standard intensity | strength is 60 N / mm < ² > or more. In this embodiment, the column 1 is a reinforced concrete structure (RC), but may be a steel reinforced concrete structure (SRC).

  The beam 2 has a reinforced concrete structure, a plurality of beam main bars 2a, 2a,... Arranged in the lateral direction, and a plurality of compressive force bearing bars 2b, 2b,... Arranged along the beam main bar 2a. , And a plurality of ribs 2c, 2c,... Arranged so as to surround the beam main bars 2a, 2a,.

  The beam 2 of the present embodiment is constructed by a half precast method, and includes a precast region 21 and a cast-in region 22 as shown in FIG.

The precast region 21 is a region where the half precast member P is disposed, and in this embodiment, the precast region 21 is provided so as to include the lower half portion of the center portion of the span of the beam 2. Although there is no restriction | limiting in particular in the height dimension of the precast area | region 21, In this embodiment, it is the value which deducted the thickness dimension of the floor slab 3 from the beam fault of the beam 2. FIG. The concrete in the precast region 21 (half precast member P) is a concrete having a normal strength (design standard strength: 36 N / mm ² or less). In this embodiment, the concrete is equal to the design standard strength of the concrete required for the floor slab 3. It has become.

The cast-in-place area 22 is an area where cast-in-place concrete is cast. In the present embodiment, the cast-in-place concrete area 22 is provided at the longitudinal end of the beam 2 and above the precast area 21. The concrete in the cast-in area 22 is a normal strength (design standard strength: 36 N / mm ² or less) concrete, and in this embodiment, is equal to the concrete design standard strength required for the floor slab 3. That is, in this embodiment, the concrete design standard strength in the cast-in area 22 is equal to the concrete design standard strength in the precast area 21 and the floor slab 3.

  Note that the concrete design standard strength at the end portion in the longitudinal direction of the beam 2 is a part of the compressive force generated at the end portion in the longitudinal direction of the beam 2 due to the bending moment acting on the beam 2. 2b is set in consideration of the structural design.

  The beam main reinforcement 2a is arranged so as to cross the boundary surface J between the column 1 and the beam 2 so that a tensile force generated on the boundary surface J can be borne. When the beams 2 are formed on both sides of the column 1, the beam main reinforcing bars 2 a may be extended not only to one beam 2 but also to the other beam and shared by the two beams 2. Note that it is not necessary to form the beam main reinforcing bar 2a with a single reinforcing bar, but a beam obtained by connecting a plurality of reinforcing bars in the axial direction via a joint t formed by enclose welding, a mechanical joint, or the like. The main muscle 2a may be used.

  The position, number, nominal diameter, etc. of the beam main reinforcing bars 2a are appropriately changed according to the bending strength required for the beam 2, but in the present embodiment, the same number is arranged on the upper side and the lower side of the beam 2. (See (b) of FIG. 1). A part of the lower beam main bar (lower bar) 2a is embedded in the half precast member P, and the remaining part protrudes from the end surface of the half precast member P. The upper beam main bar (upper bar) 2a is arranged above the half precast member P, and is entirely exposed until concrete is placed in the cast-in-place region 22.

  The compressive force bearing reinforcing bar 2b is a reinforcing bar different from the beam main reinforcing bar 2a so that it can bear a part of the compressive force generated at the end portion in the longitudinal direction of the beam 2 due to the bending moment acting on the beam 2. The bar 2 is arranged at the end in the longitudinal direction. Further, the compressive force bearing rebar 2b is arranged so as not to cross the boundary surface J so as not to bear the tensile force generated on the boundary surface J. The compressive force bearing rebar 2b of the present embodiment is disposed only at the longitudinal end of the beam 2 included in the cast-in area 22 and overlaps with the beam main bar 2a in the cast-in area 22. More specifically, the compressive force-bearing reinforcing bar 2b is disposed between the vertical plane V and the vertical plane V passing through a position separated from the boundary plane J by a distance α, and between the boundary plane J and the vertical plane V. It is parallel to the beam main reinforcement 2a. Since the hinge region at the end in the longitudinal direction of the beam 2 is generally a region that is about 1.0 to 1.5 times as long as the beam from the boundary surface J, the beam 1 It is desirable to arrange the compressive force bearing rebar 2b between the vertical plane V passing through a position separated from the boundary plane J by a length of 0.0 to 1.5 times and the boundary plane J. Further, it is desirable that the end of the compressive force-bearing reinforcing bar 2b on the column 1 side coincides with the boundary surface J.

  The position, number, nominal diameter, etc. of the compressive force bearing rebar 2b are appropriately changed according to the bending strength required for the beam 2, but the compressive force bearing rebar 2b of the present embodiment is affected by the seismic load. When a bending moment is applied such that the upper end of the beam 2 is on the tension side and the lower end is on the compression side, the same diameter and the same number as the lower beam main reinforcement 2a, which is a compression reinforcing bar, and the inner circumference side of the rib 2c Are arranged above the lower beam main bars 2a, 2a,... (See FIG. 1B). More specifically, the compressive force bearing reinforcing bar 2b is disposed immediately above the lower beam main reinforcing bar 2a, and is fixed to the beam main reinforcing bar 2a by a not-shown wire or the like in contact with the beam main reinforcing bar 2a.

  The stirrup 2c may be appropriately arranged according to the shear strength required for the beam 2 and the like. A part of the stirrup 2c arranged in the precast region 21 is embedded in the half precast member P, and the remaining part protrudes from the upper surface of the half precast member P. Further, the rib 2c arranged in the cast-in area 22 is arranged so as to surround the beam main reinforcing bar 2a and the compressive force-bearing reinforcing bar 2b (see FIG. 1B), and the cast-in area 22 includes concrete. Until it is placed, all of it is exposed.

The floor slab 3 has a reinforced concrete structure, includes a slab reinforcement (not shown), and is connected to an upper side surface of the beam 2 as shown in FIG. The concrete of the floor slab 3 is a concrete having a normal strength (design standard strength: 36 N / mm ² or less). Of the concrete of the floor slab 3, the concrete located in the regions 3 a and 3 a adjacent to the beam 2 bears a part of the compressive force generated in the beam 2 due to the bending moment acting on the beam 2.

  According to the column beam frame K1 described above, a part of the compressive force generated in the vicinity of the boundary surface J is compressed when a bending moment is applied such that the upper end of the beam 2 is on the tension side and the lower end is on the compression side. Since the force-bearing reinforcing bar 2b comes to bear, the compressive force to be borne by the concrete on the compression side of the beam 2 is smaller than that of a conventional column beam frame that does not place the compressive-force bearing reinforcing bar 2b. That is, according to the column beam frame K1, it is possible to use normal strength concrete which is cheaper than high strength concrete for the beam 2, and thus it is possible to keep material costs low.

  That is, if the tensile reinforcement ratio (= cross-sectional area of tensile reinforcement / (beam width x effective beam length)) is the same, the larger the double reinforcement ratio (= compression reinforcement cross-sectional area / tensile reinforcement cross-sectional area), the more demanded for concrete. When the compressive strength is reduced, in the column beam frame K1, when a bending moment is applied by the seismic load so that the upper end of the beam 2 is on the tension side and the lower end is on the compression side, the tensile reinforcement 4 of the beam main bar 2a at the upper end. On the other hand, a total of eight beams, the lower beam main bar 2a and the compressive force bearing rebar 2b, are effective as compression reinforcing bars, and the compressive force borne by the compression concrete on the lower end is smaller than that of the conventional column beam frame. Become. On the other hand, when a seismic load is applied in the opposite direction, that is, when a bending moment is applied such that the upper end of the beam 2 is on the compression side and the lower end is on the tension side, the compressive force bearing rebar that does not cross the boundary surface J. Since 2b does not bear the tensile force generated at the boundary surface J, there are only four reinforcing bars of the beam main reinforcing bar 2a at the lower end, and the tensile reinforcing bar ratio does not change. In this case, there are only four reinforcing bars of the beam main reinforcing bar 2a at the upper end, but the compressive force generated at the upper end is not only the compression side concrete of the beam 2, but also the concrete in the areas 3a and 3a of the floor slab 3. Therefore, there is no problem even if the compressive force bearing rebar 2b is not arranged on the upper side of the beam 2.

The advantages of the column beam frame K1 will be described in more detail.
According to “Reinforced Concrete Structure Calculation Criteria and Explanation -Allowable Stress Degree Design Method 1999” of the Architectural Institute of Japan, the balanced rebar ratio P _tb can be obtained by the following equation (1).

Since it is to be avoided that the bending strength is determined in the case of brittle concrete, it is usual to determine the bending strength by the beam main bar on the tension side. That is, it should become tensile reinforcement amount from tensile reinforcement ratio _{p t (= a t / (} bd); b Liang width) calculates a relationship equation between the balance reinforcement ratio _{p tb} of formula (1) (2 Usually, the concrete strength is determined so as to satisfy.
p _t ≦ p _tb (2)

As a comparative example, assuming a beam 2 ′ as shown in FIG. 2A, the balanced rebar ratio p _tb is calculated as shown in Table 1 using Equation (1). In the beam 2 ′, four main beam bars 2 a ′ having the same diameter are arranged in the vertical direction, so that the double reinforcement ratio γ is 1.0. The type of the beam main reinforcement 2a' is the SD590 (allowable tensile stress of ^{_{f t = 590N / mm 2)}} , nickname is D38 (nominal cross-sectional area = 1140 mm ^2). Allowable compressive stress of f _c and the Young's modulus ratio n of concrete, above the Architectural Institute of Japan are those that were calculated in accordance with the "reinforced concrete structure calculation criteria, the same commentary - 1999 - allowable stress design method".

Tensile reinforcement cross-sectional area _{a t} of the beam 2 'is 1140 mm ² × 4 present = 4560mm ^2, 550mm beamed width b of the beam 2', since the effective beam depth d is 720 mm, reinforcement ratio _{p t} is
p _t = 4560 / (550 × 720) × 100 = 1.15 (%)
It is. Therefore, the beams 2 'in order to satisfy the condition of formula (2), it is necessary to the design strength _{F c} of the concrete of the beam 2' and 42N / mm ² (see Table 1).

On the other hand, when the lower end of the beam 2 according to the present embodiment is on the compression side, the floor slab 3 is omitted, and the same as the lower beam main reinforcement 2a as shown in FIG. since the Haisuji compressive force share rebar 2b diameter and the same number (four), the compression rebar sectional area a _c of the beam 2, but twice the beam 2 ', the tensile reinforcement cross-sectional area a _t the upper end The double muscle ratio γ is 2.0. When the balanced reinforcing bar ratio p _tb is calculated by the equation (1) with the double reinforcing bar ratio γ being 2.0, it is as shown in Table 2.

According to Table 2, design strength _{F c} satisfies the condition concrete of formula (2) may can be seen that 30 N / mm ^2. Incidentally, as described above, the tensile reinforcement cross-sectional area _{a t} of the beam 2, since no different from that of beam 2 ', reinforcement ratio _{p t} of the beam 2 is 1.15 (%).

  Thus, according to the column beam frame K1 according to the present embodiment, the compressive strength of the concrete required for the beam 2 is smaller than that required for the beam 2 ′ of the comparative example. It becomes possible to use ordinary strength concrete which is cheaper than the high strength concrete used in 2 ′.

  Moreover, in this embodiment, since the concrete of the same strength is used for the beam 2 and the floor slab 3, it becomes possible to place concrete on the beam 2 and the floor slab 3 at the same time. That is, there is no need to separate the concrete between the beam 2 and the floor slab 3, and the installation and demolding work of the mold necessary for the placement is not required.

  Furthermore, in the present embodiment, the compressive force bearing rebar 2b is arranged only at the longitudinal end of the beam 2, so that the amount of arrangement of the beam 2 is prevented from being increased more than necessary. It becomes possible to keep the labor cost required for the bar arrangement work low.

In addition, you may change suitably the position of the compressive-force burden reinforcement 2b, the number, the magnitude | size of a cross-sectional area, etc.
For example, in this embodiment, the floor slab 3 is connected to the upper side surface of the beam 2, and the compressive force generated by the concrete in the regions 3 a and 3 a adjacent to the beam 2 is caused by the bending moment of the beam 2. As shown in FIG. 3, the floor slab 3 is connected to the lower side surface of the beam 2 and the concrete in the areas 3a and 3a adjacent to the beam 2 is made of the beam. When a part of the compressive force generated in the beam 2 due to the bending moment of 2 is borne, the compressive force-bearing reinforcing bars 2b, 2b,... Are superimposed on the upper beam main bars 2a, 2a,. .

  Moreover, in this embodiment, although the case where the floor slab 3 was provided was illustrated, when the floor slab 3 does not exist (or when the concrete of the floor slab 3 does not bear the compressive force generated due to the bending moment). Since a large compressive force is applied to the upper half of the beam 2 due to repeated positive and negative seismic loads, only the upper side of the lower beam main bars 2a, 2a,..., As shown in FIG. However, the compression load bearing rebar 2b is also arranged below the upper beam main bars 2a, 2a,.

  In FIG. 4A, the compressive force-bearing rebar 2b is arranged directly above or directly below the beam main reinforcing bar 2a. However, like the compressive force-bearing rebar 2b on the lower side of FIG. You may arrange | position just beside.

  In FIG. 4A, the compressive force bearing reinforcing bar 2b is in contact with the beam main reinforcing bar 2a. However, as shown in FIG. 4B, the compressive force bearing reinforcing bar 2b is separated from the main beam reinforcing bar 2a. You may let them.

  4 (a), the number of compressive force bearing rebars 2b is the same as the number of beam main bars 2a. However, as shown in FIGS. Also good. In addition, in (b) and (c) of FIG. 4, although the number of the compressive-force burden reinforcement 2b is less than the beam main reinforcement 2a, you may increase it.

  4 (a) and 4 (b), the compressive force bearing rebar 2b has the same diameter as the beam main reinforcing bar 2a, but like the compressive force bearing rebar 2b on the upper side of FIG. 4 (c), It may be different from the beam main reinforcement 2a. In FIG. 4C, the nominal diameter of the upper compressive force bearing reinforcing bar 2b is larger than that of the upper beam main reinforcing bar 2a, but may be smaller.

(Second embodiment)
The column beam frame K2 according to the second embodiment includes the column 1 and the beam 5 as shown in FIG. The floor slab 3 is integrally connected to the upper side surface of the beam 5 as shown in FIG.

  In addition, since the structure of the pillar 1 and the floor slab 3 is the same as that of the thing of 1st embodiment, the detailed description is abbreviate | omitted.

  The beam 5 has a reinforced concrete structure, and a plurality of first beam main bars 5a, 5a,... Arranged in the horizontal direction, and a plurality of second beam main bars 5b, 5b,. Are composed of a plurality of stirrups 5c, 5c,... Arranged so as to surround the second beam main bars 5b, 5b,.

  The beam 5 is constructed by a half precast method, and includes a precast area 51 and a cast-in area 52. The configurations of the precast area 51 and the place-in-place area 52 are the same as those of the precast area 21 and the place-in-place area 22 in the first embodiment, respectively, and thus detailed description thereof is omitted.

  The first beam main reinforcement 5a is arranged so as to cross the boundary surface J between the column 1 and the beam 5 so that a tensile force generated on the boundary surface J can be borne. In addition, when the beam 5 is formed on both sides across the column 1, the first beam main reinforcing bar 5 a may be arranged so as to straddle the two beams 5. The position and number of the first beam main reinforcing bars 5a are appropriately changed according to the bending strength required for the beams 5, but in this embodiment, the same number of bars are arranged on the upper side and the lower side of the beams 5. (See FIG. 5B).

  The second beam main reinforcement 5b is arranged so as not to cross the boundary surface J so as not to bear the tensile force generated on the boundary surface J. The second beam main reinforcing bar 5 b of the present embodiment is arranged over the entire length of the beam 5 and overlaps the first beam main reinforcing bar 5 a in the place-in-place region 52. In addition, the overlap length of the 1st beam main reinforcement 5a and the 2nd beam main reinforcement 5b is ensured more than the length in which all the lap joints are formed in a beam end part.

  A part of the lower second beam main reinforcing bar 5 b is embedded in the half precast member P, and the remaining part protrudes from the end face of the half precast member P. The upper second beam main reinforcing bar 5b is arranged above the half precast member P, and is entirely exposed until concrete is placed in the place-in-place region 52.

  The position, number, nominal diameter, and the like of the second beam main bar 5b are appropriately changed according to the bending strength required for the beam 5, but the second beam main bar 5b of the present embodiment is the first beam main bar 5b. It has the same diameter and the same number as the main muscle 5a. The lower second beam main bars 5b, 5b,... Are arranged below the lower first beam main bars 5a, 5a,..., And the upper second beam main bars 5b, 5b,. The bars are arranged above the first beam main bars 5a, 5a,... (See FIG. 5B).

  The stirrup 5c may be appropriately arranged according to the shear strength required for the beam 5 and the like. A part of the stirrup 5c arranged in the precast region 51 is embedded in the half precast member P, and the remaining part protrudes from the upper surface of the half precast member P. Further, the stirrup 5c arranged in the place hitting region 52 is arranged so as to surround the first beam main reinforcing bar 5a and the second beam main reinforcing bar 5b (see FIG. 5B).

In addition, the design standard strength of the concrete at the end portion in the longitudinal direction of the beam 5 is a part of the compressive force generated at the end portion in the longitudinal direction of the beam 5 due to the bending moment acting on the beam 5. It is set in consideration of structural design that the second beam main bar 5b bears in addition to the main bar 5a. The design standard strength of the concrete used for the beam 5 of this embodiment is 36 N / mm ² or less, and is equal to the design standard strength of the concrete used for the floor slab 3.

  According to the column beam frame K2 described above, the first beam main reinforcement 5a and the second beam main reinforcement 5b bear the compressive force generated in the vicinity of the boundary surface J. Since the second beam main bar 5b does not cross the boundary surface J, the tensile reinforcing bar cross-sectional area at the boundary surface J does not increase. That is, according to the column beam frame K2, the double reinforcement ratio of the beam 5 can be increased without increasing the tensile reinforcement ratio of the beam 5 at the boundary surface J. Therefore, the compressive force that the concrete of the beam 5 should bear Is smaller than the conventional column beam structure. That is, according to the column beam frame K2, it is possible to use normal-strength concrete that is cheaper than high-strength concrete, and thus it is possible to keep material costs low.

  Moreover, in this embodiment, since the same strength concrete is used for the beam 5 and the floor slab 3, it becomes possible to place concrete on the beam 5 and the floor slab 3 at the same time. That is, it is not necessary to separate the concrete between the beam 5 and the floor slab 3, and the installation and demolding work of the mold necessary for the placement is not required.

  In the present embodiment, the first beam main reinforcing bar 5a and the second beam main reinforcing bar 5b are overlapped at the longitudinal end of the beam 5, but the first beam main reinforcing bar 5a extends in the center direction of the beam 2. For example, the first beam main reinforcement 5a and the second beam main reinforcement 5b may be overlapped over the entire length of the beam 5.

  Further, as shown in FIGS. 6A and 6B, a compressive-force bearing reinforcing bar 5d different from the first beam main reinforcing bar 5a and the second beam main reinforcing bar 5b is arranged at the end of the beam 5 in the longitudinal direction. May be. When the compressive force bearing reinforcing bar 5d is used in combination, the end of the second beam main reinforcing bar 5b may be separated from the boundary surface J.

  In each of the above-described embodiments, the case where the beams 2 and 5 that have been half-precasted are used as an example is illustrated, but even if a compressive force bearing rebar or the second beam main bar is incorporated into the beam that has been fully precasted. Of course, it is possible to incorporate a compressive-force bearing reinforcing bar or a second beam main reinforcing bar into a beam that is not precast (that is, a beam composed entirely of cast-in-place concrete).

(A) is sectional drawing for demonstrating the column beam frame which concerns on 1st embodiment, (b) is BB sectional drawing of (a). (A) is sectional drawing of the beam which concerns on a comparative example, (b) is sectional drawing of the beam in the column beam frame which concerns on 1st embodiment. It is sectional drawing for demonstrating the modification of the column beam frame which concerns on 1st embodiment. (A)-(c) is sectional drawing for demonstrating the other modification of the column beam frame which concerns on 1st embodiment. (A) is sectional drawing for demonstrating the column beam frame concerning 2nd embodiment, (b) is the BB sectional drawing of (a). (A) is sectional drawing for demonstrating the modification of the column beam frame which concerns on 2nd embodiment, (b) is the BB sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Column 2 Beam 2a Beam main reinforcement 2b Compression load bearing rebar 21 Precast area 22 Cast-in area 3 Floor slab 5 Beam 5a First beam main reinforcement 5b Second beam main reinforcement 5d Compression force bearing reinforcement J Boundary plane V Vertical plane K1, K2 Column beam Frame

Claims (4)

A first beam main bar that crosses the boundary surface between the column and the beam, and a second beam main bar that does not cross the boundary surface;
A column beam structure of a reinforced concrete structure in which the first beam main reinforcement and the second beam main reinforcement are overlapped at the longitudinal end of the beam,
Considering that the second beam main bar bears a part of the compressive force generated at the longitudinal end of the beam due to the bending moment acting on the beam, the longitudinal direction of the beam A column beam frame characterized by the fact that the design standard strength of concrete is set at the end of the building. Providing a beam main bar and a compressive force bearing reinforcing bar different from the beam main bar,
A column beam structure of a reinforced concrete structure in which the beam main reinforcing bar and the compressive force bearing reinforcing bar are overlapped at the end in the longitudinal direction of the beam,
The compressive force bearing rebar is provided so as not to cross the interface between the column and the beam,
In consideration of the structural design, the longitudinal direction of the beam in consideration of the fact that the compressive force bearing rebar bears a part of the compressive force generated at the longitudinal end of the beam due to the bending moment acting on the beam. A column beam frame characterized by the fact that the design standard strength of concrete is set at the end of the building. A first beam main bar that crosses the boundary surface between the column and the beam, and a second beam main bar that does not cross the boundary surface;
A column beam structure of a reinforced concrete structure in which the first beam main reinforcement and the second beam main reinforcement are overlapped at the longitudinal end of the beam,
The design standard strength of the concrete used for the pillar is 60 N / mm ² or more,
The design standard strength of the concrete used for the end portion in the longitudinal direction of the beam is 36 N / mm ² or less, and the concrete design standard used for the floor slab of the reinforced concrete structure connected to the side surface of the beam. A column beam structure characterized by equal strength. Providing a beam main bar and a compressive force bearing reinforcing bar different from the beam main bar,
A column beam structure of a reinforced concrete structure in which the beam main reinforcing bar and the compressive force bearing reinforcing bar are overlapped at the end in the longitudinal direction of the beam,
The compressive force bearing rebar is provided so as not to cross the interface between the column and the beam,
Column beam characterized in that the design standard strength of concrete used for the longitudinal end of the beam is equal to the design standard strength of concrete used for a floor slab of a reinforced concrete structure connected to the side of the beam Frame.

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